id say you need a .357mag or larger revolver for just in case you had an encounter with a wild animal/large or dangerous game.
replace or supplement the nylon rope for some 550paracord
a large fixed balde knife, those swiss army knives are nice to carry everday but not too good once you are away from civilization.
how about some glow sticks? decent light and last 24hours
signal mirror
some duct tape rolled up on an old credit card to make it more compact
take as much water as you can, preferrably in 20oz or so bottles.
a shotgun is a possibility, if you can fit it and some shells take it. remember if its a 870 or the like, you can take the barrel off and probably fit it in a backpack concealed, and have it together in about a minute.
a .22 pistol would be VERY valuable if you were to have to hunt for food.
a high-powered takedown rifle might be valuable too, like a ar or a NEF single shot. something to possibly defend yourself with or hunt with.
roll of black electrical tape is almost as useful as duct tape
if you think there might be a civilization to come back to, might be wise to take some copies of important papers like drivers licenses, birth certificates, deeds, titles, etc. some people who left hurricane katrina and went somewhere else had trouble proving who they were in a different town in order to get work or whatever, just something to think about.
knife sharpener
gun cleaning kit
gloves
GI whistle
cb or ham radio
maybe a police scanner